锂离子电池英语论文

Octadecylamineoxideasthetemplatesynthesisoflithiatedvanadiumoxideshalfopened-nanotubesSynthesisofLithiatedVanadiumOxidesHalfOpened-nanotubesasCathodeMaterialsforLithiumIonBatteriesJunliSun*InstituteofScienceandResearch,DepartmentofScienceandResearch,ChinesePeople’sArmedPoliceForceAcademy,220XihuanRoad,AnciDistrict,LangfangCity,HebeiProvince(065000),China.Tel[phone]AbstractThelithiatedvanadiumoxideshalfopened-nanotubes(HOT)aresynthesizedbyusingsolid-stateandsolvothermalreactionwithoctadecylamineoxideasthetemplate.Transmissionelectronmicroscopy(TEM)andscanningelectronmicroscopy(SEM)characterizationsshowthatthesynthesizedlithiatedvanadiumoxidesnanotubesarehalfopenedandagglomerate.X-raydiffraction(XRD)investigationdemonstratesthatthesynthesizedhalfopened-nanotubesaremostconsistedofmonoclinicphaseLiV3O8.Cyclicvoltammetry(CV)testindicatesthatsomeredoxprocessesarehindered,whichispropitioustoimproveelectrochemicalperformanceofLiV3O8cathodematerial.Keywords:electrochemicalproperties;nanostructures;SEM;TEMIntroductionNanostructuredcathodeandanodematerialsinlithiumionbatterieshaveattractedgreatattention.Thisisbecausetheyshowhighercapacitythanconventional*Correspondingauthor.Tel.:[phone];Fax:[phone]E-mailaddresses:[e-mail]esamematerials,andthesurfaceareaofnanostructuredelectrodesismuchlargerthanthatofconventionalelectrodes.Vanadiumoxideshavebeenwidelystudiedascathodeactivematerialsinlithiumrechargeablebatteriesbecauseoftheirlowcostandhightheorycapacity[1-6].ChenWetal.usethetemplatehydrothermaltreatmenttosynthesizeV2O5nanotubes.Whentheyareusedascathode,theresultingcellhasshowninitialdischargespecificcapacityof306mAhg-1at3.6-1.5V,whichissignificantlysuperiortothatofmaterialspreparedbyconventionalmethods.Thisnanotubecanmaintain80%ofitsinitialcapacity[7].ButtherewerenoreportsaboutanymethodstoprocessLiV3O8halfopened-nanotubeselectrodematerial.Inthiswork,high-orderedLiV3O8halfopened-nanotubesarraysaresynthesizedbyusingThesolid-stateandsolvothermalreactionwithoctadecylamineoxideasthetemplate.Octadecylamine(18胺)Cetyltrimethylammoniumbromide(CTAB)2ExperimentalAllofthechemicalreagentswereofanalyticalgradeandusedwithoutfurtherpurification.1.V2O5(0.06mol)wasaddedto25ml30%(w/w)H2O2aqueoussolution,andtheresultingmixturewasstirredfor2h.Then,0.04molmixtures(LiOH·H2OandAgNO3withdifferentmolratios)wereaddedinadesiredstoichiometricratio,togetherwith15mlof1mol/LHNO3aqueoussolution.PHmeasurementisperformedwithapHmeterusing2.4forcalibration.Aftercontinuousstirringfor2hours,theresultingprecursorsuspensionwastransferredintoa100mLTeflon-linedautoclaveandmaintainedat180°Cforacertaintime.Afterbeingcooledtoambienttemperaturenaturally,thesolutionintheautoclavewascollectedandfinallyvacuum-driedat100°Cfor12h.Finallythesolidpowderwascalcinedatcertaintemperaturesfor16hours.Forcomparison,withouthydrothermalroute,LiV3O8particleswerealsocalcinedat400°Cfor16hours.2.2.MeasurementsThecompositecathodes(mg/cm2)werepreparedbypressingthemixtureoftheactivematerials,conductivematerial(acetyleneblack)andbinder(PTFE)inaweightratioof8/1/1.TheLimetalwasusedasthecounterandreferenceelectrodes.Theelectrolytewas1MLiPF6ina6/3/1(volumeratio)mixtureofethylenecarbonate(EC),propylenecarbonate(PC)anddimethylcarbonate(DMC).Thegalvanostaticmethodwasemployedtomeasuretheelectrochemicalcapacityofthesamplesatacurrentdensityof60mAg-1,withthesamecut-offvoltages(1.8-4.0V)forchargeanddischargeprocesses,respectively.AlltestswereperformedatroomtemperatureX-raypowderdiffraction(XRD)wascarriedoutusingXRD(D/Max-2500).ScanningElectronMicroscopy(SEM)measurementswerecarriedoutonaHitachiS-570microscope.CHI660belectrochemicalworkstationwasusedtotestCyclicvoltammetry(CV)(scanrate:0.1mVs−1,cutoffvoltage:1.8–4.0V)measurements.Fig.1.SEMandTEMimagesofLiV3O8halfopened-nanotubesFig.1showsthemorphologyofLiV3O8halfopened-nanotubes.FortheLiV3O8halfopened-nanotubespowders,NanotubesareclearlyobservedonthesurfacesofLiV3O8particles.Themorphologyof1.0wt.%LiV3O8halfopened-nanotubesand2.0wt.%LiV3O8halfopened-nanotubesaremuchdifferenttobareLiV3O8.LiV3O8particlesarecoatedbyAlPO4nanowiresuniformlyat1.0wt.%AlPO4coating.Whenthecoatingamountincreaseto2.0wt.%,manyAlPO4nanowirescanbeobservedonthesurfaceofLiV3O8particles,butitalsocanbefoundthatsomeAlPO4compoundisformedaslittleparticles.Inthecaseofthe3.0wt.%AlPO4coating,LiV3O8particleswerecoatedmainlybyAlPO4particlesandonlyfewAlPO4nanowirescanbeobserved.ItsBADCBmorphologyissimilartobareLiV3O8.ThereasonisthattoomuchconcentrationoftheAlPO4-nanoparticlesolutionwillnotbepropitioustoformationofAlPO4nanowires.IthasbeenreportedbymanyresearchersthatsurfacemorphologyisanimportantfactorforelectrochemicalperformancesofLiV3O8.TheTEMmicrographsof1.0wt.%LiV3O8halfopened-nanotubesisshowninFig.3.AlPO4coatedonitssurfacepresentsawellnanowires(aboutΦ40nmand0.5~2μmlong)morphology.OneendofAlPO4nanowiresisoutwardandvisible,whileanotherendofitisinvisibleandintegratesintoLiV3O8matrix.AlPO4willpartillayreactwithLiV3O8toformasolidsolutioni